I love eggs. Come to think of it, I’ve never met an egg I didn’t like. Hard or soft, salty or bland, alone, within, or beside something else. Few foods given to us by nature—particularly ones packing the egg’s powerful nutritional punch—come in such handy, self-contained packages as these oblate spheroids.
As I made breakfast one morning, I could not help but wonder how cooking an egg almost instantly turns slimy, transparent ooze into an opaque, white solid. Curiously, only after the deliberate addition of heat by humans does the egg white actually become white. Uncooked, as it exists in nature, shouldn’t it be called “the egg clear?” And just what purposes do this phase-shifting mucus and its sun-colored counterpart serve for chickens?
The white, or albumen, (two-thirds of an egg’s unshelled mass) nourishes a tiny germ cell that will grow into that clucking, pecking bird. The germ cell—the bead-sized white nodule attached to the yolk, visible when you crack open a raw egg—contains all of the mother hen’s genetic information, necessary to pass her chicken-ness into her progeny. If fertilized, a chick results.
The flaxen yolk, to which the germ cell clings, rests suspended in the center of the white thanks to two flexible, fibrous cords called chalazae. Much like the prongs of a rotisserie—which this fledgling chicken might confront later in life—the chalazae fix themselves to the ends of the shell, thus holding the yolk and germ cell in place in the protective, viscous pond of white. A cache of nutrients consumed and stockpiled by the mother hen, the marigold yolk feeds proteins, vitamins, and minerals to the soon-to-be feathered organism. The blob’s golden hue, created by a plant pigment called xanthophyll in the alfalfa and corn of the hen’s diet, reflects the stored energy of the sun. “An egg is the sun’s light refracted into life,” wrote Harold McGee in his book On Food and Cooking. Plants, the silos holding all that solar energy, compose the foundation of the food chain.
The key to the egg’s metamorphosis in a frying pan, and its versatility in countless culinary delights, is the collection of floating proteins in the albumen. Like long, tightly crumpled strips of paper, folded upon themselves, the proteins drift slowly within the aqueous liquid, occasionally bumping into each other. For every lonely protein molecule, about 1,000 water molecules linger nearby. Add some heat, however, and the lumbering proteins begin to dance frenetically. If you shook a container full of crumpled paper strips, they would barrel into each other, gradually unraveling into lengthy threads. The same is true of egg proteins. With heat, keeping their distance from each other becomes problematic, then impossible.
As the heat increases, the proteins ensnare and entangle each other into a protein network that rapidly grows outward from the first few marriages of molecules. And these energized proteins make friends at breakneck speed. The egg white solidifies, and the hapless water molecules find themselves trapped in the tightening lattice. The combination of water and protein creates a moist solid. Unlike the floating protein and water solution of an uncooked albumen, this dense lattice reflects light, turning the clear goo its characteristic white.
To the dismay of even the most talented chefs, overcooking the somewhat temperamental egg leads to a rubbery or lumpy texture. With gentle heating, the protein molecules essentially agree to hold hands, embrace water molecules, sing Kumbaya, and create a supple, agreeable protein network. Add too much heat, however, and the proteins form cliques, bonding so closely, so steadfastly that they expel the trapped water molecules, forming hardened lumps and runny liquid.
The intact yolk, a sac of squishy globules misshapen from overcrowding, turns granular when cooked because each flattened globule hardens into the distorted shape imposed upon it by the yolk membrane. Breaking the yolk, say, to whip up a bunch of scrambled eggs, allows the globules to spread out, expanding and sliding against each other freely. Mix the white and yolk together, heat the combination gently, and the resulting open but delicate framework lends custard, such as Crème Brulee, its fragile, silken texture.
It’s difficult to envision a world without eggs, the basis for so many modern foods. Most baked goods couldn’t exist, glued together, as they are, by the cooked protein mesh, which holds fixed the various components of a muffin or quiche. No Hollandaise, often referred to as “the mother sauce,” would drape our roasts or Eggs Benedict. What would replace pasta, ice cream, eggnog, omelets, flan and cheesecake on our restaurant menus and dinner tables?
Fear not. Eggs are inextricably connected to culinary traditions around the world, and they will likely remain that way for some time. Hens work very hard, annually converting eight times their body weight into eggs, to ensure that no mayonnaise shortage looms in the near future. Nearly 300 potential fuzzy yellow offspring every year? Or 300 mornings that I can watch eggs white on my kitchen stove. Now that’s impressive.
